#include <iostream>
#include <string>
#include <unordered_map>
using namespace std;

int main() {
    int n;
    while (scanf("%d", &n) && n != 0) {
        unordered_map<string, int> count;
        
        for (int i = 0; i < 2 * n - 1; i++) {
            char name[25];  // 考虑到汉字占2个字节，预留足够空间
            scanf("%s", name);
            string str_name(name);
            count[str_name]++;
        }
        
        // 找出出现次数为奇数的姓名（即缺席的人）
        for (auto& pair : count) {
            if (pair.second % 2 == 1) {
                cout << pair.first << endl;
                break;
            }
        }
    }
    
    return 0;
}